Proteus Cave Vivarium

The undisputed star among inhabitants of the Postojna Cave is the olm, Proteus anguinus, also known as the human fish, however the Karst underground world is inhabited by a large number of other interesting inhabitants.

According to explorers' estimates, the Postojna Cave provides shelter to more than 150 animal species – visitors can get to know some of the most interesting ones in more detail in the Vivarium Proteus.

The Postojna Cave is the cradle of a special branch of biology – speleobiology. This new science was born in the year 1831, when the Slendernecked Beetle (Leptodirus hochenwarti) was discovered in the Postojna Cave by Luka Čeč, a local of Postojna. Not long after, explorers discovered and made an inventory of tens of new animal species adapted to the conditions inside the cave to such an extent that they are unable to survive outside of it.

Vivarium Proteus is located inside the Passage of New Signatures, 50 metres from the entrance into the Postojna Cave. It consists of two sections – the research section and the exhibition one. The research section, the so-called laboratory, is used for scientific work and research. And the speleobiological exhibition housed within the exhibition section introduces visitors to the basic concepts of karstology and speleobiology in an appealing way, and presents special features of the subterranean environment and the most characteristic representative of Slovene cave animals. Most attention is however devoted to the human fish (the olm / Proteus anguinus).

The Human Fish (Proteus anguinus)

The proteus, also known as the olm or the human fish, is the largest cave-dwelling animal. It is 25 to 30 centimetres in length and is the only vertebrate in Europe that lives solely in the subterranean world.

It is extremely well-adapted to life in darkness – its skin lacks any protective pigmentation, and the blood showing through it makes it very pale or slightly pink in colour. It was given the name human fish because of the colour of its skin, which resembles the skin of people. Its eyes are undeveloped.

It breathes with external gills, as well as with rudimentary lungs and the skin. It has an inner ear, which serves both the purposes of balance and hearing. It has two pairs of tiny legs, which are relatively far apart. Its front legs have three digits and the rear ones have two. Its tail surrounded by a thin fin makes it possible for the proteus to swim.

It feeds on small crabs, worms, snails and other aquatic non-vertebrates. It has a life expectancy of up to 100 years and can survive without food for several years in a row. It is reproduced by means of eggs, which females lay on the bottom side of flat stones.

In Slovenia, the proteus is under strict legal protection and was in 1982 placed on a list of rare and endangered species. It is forbidden to catch the proteus without a special consent given by the competent environmental institutions.